1. Field of the Invention
The invention provides, as an integrated circuit, a logic inverter using field-effect transistors with a low threshold voltage as well as a switching diode.
2. Description of the Prior Art
So-called "normally on" field-effect transistors and "normally off" transistors are conventional. The first are pinched off by depletion, requiring a double-polarity supply and presenting furthermore the disadvantage of electric current consumption in the rest condition. The latter let the current pass when an appropriate voltage is applied to the control gate: they do not require a double-polarity power supply and are more economical, but on the contrary difficult to produce, because of the very small thickness of the conducting channel which gives rise to a large amount of manufacturing waste.
A third category of field-effect transistors, which is intermediate between the two preceding ones while approximating to the second one, is formed by the quasi normally off transistors: they are off for a threshold voltage V.sub.T which may be positive or negative, which means that a certain amount of dispersion is admitted in the collective manufacture of these transistors which is for example the following: EQU -0.5.ltoreq.V.sub.T .ltoreq.0.2 volt
This category suffers certain drawbacks. In particular:
1. In this technology, there is formed on the same integrated-circuit wafer grooved channel structures some of which form saturable loads of the logic circuits and others, after metalization of the groove, the field-effect transistors. It is difficult, because of the dispersion of the characteristics, to obtain good reproductivity of the logic circuits thus formed.
2. Because of the dispersion of the characteristics, the threshold voltage is sometimes positive, sometimes negative; in the case where it is negative, the input transistor is not pinched off, which presents, besides a drawback from the point of view of consumption, a reduction of the fan-in of the circuit preventing in particular the setting of a multiple inputs, for example in the case of the construction of gates of the "NAND" type.